on button click hover other div code example

Example 1: make action on hover on other element

#container:hover ~ #cube { background-color: yellow; }

Example 2: make action on hover on other element

#container {
  width: 200px;
  height: 30px;
  border: 1px solid var(--c);
  --c:red;
}
#container:hover {
  --c:blue;
}
#container > div {
  width: 30px;
  height: 100%;
  background-color: var(--c);
}